CVE-2026-1781
MEDIUMCVSS Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L
Lifecycle Timeline
2Tags
Description
The MC4WP: Mailchimp for WordPress plugin for WordPress is vulnerable to Missing Authorization in all versions up to, and including, 4.11.1. This is due to the plugin trusting the `_mc4wp_action` POST parameter without validation, allowing unauthenticated attackers to force the form to process unsubscribe actions instead of subscribe actions. This makes it possible for unauthenticated attackers to arbitrarily unsubscribe any email address from the connected Mailchimp audience via the `_mc4wp_action` parameter, granted they can obtain the form ID (which is publicly exposed in the HTML source).
Analysis
Unauthenticated attackers can arbitrarily unsubscribe email addresses from Mailchimp audiences through the MC4WP: Mailchimp for WordPress plugin (versions up to 4.11.1) by manipulating the unvalidated _mc4wp_action POST parameter, requiring only publicly exposed form IDs. This missing authorization vulnerability allows bulk email removal operations without authentication, impacting any WordPress site using the affected plugin with a connected Mailchimp account. …
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Remediation
Within 30 days: Identify affected systems running for WordPress is vulnerable to Missing Authorization in all and apply vendor patches as part of regular patch cycle. Monitor vendor channels for patch availability.
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